IL-18 is an IL-1 family cytokine. It acts as a pleiotropic pro-inflammatory cytokine, and it is important for host innate and adaptive immune defense against pathogenic infections. Dysregulated IL-18 activity is associated with inflammatory and autoimmune diseases (e.g. rheumatoid arthritis, Crohn's disease, MS and lupus), allergies, and neurological disorders. IL-18 and its signalling partners are protein targets for anti-inflammatory drug development.